Our intestines are home to trillions of bacteria that help us to maintain a healthy immune system. Each of the many species living in our gut performs a different function, and so is restricted to specific areas. Confined, they’re not perceived as invaders. But when containment fails, bacteria can spread to our flesh and organs. What were ‘good’ bacteria are now perceived as ‘bad’, triggering an immune response that could turn into chronic inflammation. Here we see Alcaligenes bacteria (green-dyed dots) inside a collection of specialist ‘surveillance’ cells in the small intestine of a mouse. That’s where they should be. In mice with depleted reserves of immune cells called ILCs, however, the bacteria can spread into the liver and spleen. So these ILCs play a key role in selective containment, a discovery that could lead to new ways to treat chronic inflammatory diseases in humans.
Written by Daniel Cossins
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